Using state-of-the-art laser technology, archaeologists uncovered over 60,000 previously unknown Mayan structures deep in the Guatemalan jungle, including foundations for houses, military fortifications, and elevated causeways.

The structures uncovered by the team suggest that instead of living in isolated city-states, the Mayans controlled huge territories with millions of people, industrial-scale food production, and sophisticated trade networks — on the scale of Ancient Greece or Rome.

"With this new data it’s no longer unreasonable to think that there were 10 to 15 million people there — including many living in low-lying, swampy areas that many of us had thought uninhabitable," Francisco Estrada-Belli, the lead researcher on the project, told National Geographic.

"We’ve had this western conceit that complex civilizations can’t flourish in the tropics, that the tropics are where civilizations go to die," Marcello Canuto, a Tulane University archaeologist told National Geographic.

"We now have to consider that complex societies may have formed in the tropics and made their way outward from there," he added.